The importance of matrix metalloproteinase-3 in respiratory disorders.

The matrix metalloproteinases (MMPs) encompass a family of zinc-dependent endopeptidases that are secreted into the extracellular environment or remain bound to the cell surface. While MMPs were initially identified based on their ability to degrade collagen and other components of the extracellular matrix, recent studies indicate that their non-degradative functions are physiologically paramount. In particular, MMPs are now known to participate in diverse physiological processes that control key aspects of inflammatory and immune responses and neoplasia, in part by selective triggering of cellular signaling pathways via limited proteolytic processing of extracellular and membrane-associated proteins, including cytokines and cell surface receptors. Herein, we focus on the unique roles of MMP-3 (stromelysin-1) in acute lung injury and repair, pulmonary fibrosis, and lung cancer.